- EEG processing with TESPAR for depth of anesthesia detection (2009)
- Poster presentation: Introduction Adequate anesthesia is crucial to the success of surgical interventions and subsequent recovery. Neuroscientists, surgeons, and engineers have sought to understand the impact of anesthetics on the information processing in the brain and to properly assess the level of anesthesia in an non-invasive manner. Studies have indicated a more reliable depth of anesthesia (DOA) detection if multiple parameters are employed. Indeed, commercial DOA monitors (BIS, Narcotrend, M-Entropy and A-line ARX) use more than one feature extraction method. Here, we propose TESPAR (Time Encoded Signal Processing And Recognition) a time domain signal processing technique novel to EEG DOA assessment that could enhance existing monitoring devices. ...
- Cuff overinflation and endotracheal tube obstruction : case report and experimental study (2010)
- Background: Initiated by a clinical case of critical endotracheal tube (ETT) obstruction, we aimed to determine factors that potentially contribute to the development of endotracheal tube obstruction by its inflated cuff. Prehospital climate and storage conditions were simulated. Methods: Five different disposable ETTs (6.0, 7.0, and 8.0 mm inner diameter) were exposed to ambient outside temperature for 13 months. In addition, every second of these tubes was mechanically stressed by clamping its cuffed end between the covers of a metal emergency case for 10 min. Then, all tubes were heated up to normal body temperature, placed within the cock of a syringe, followed by stepwise inflation of their cuffs to pressures of 3 kPa and >=12 kPa, respectively. The inner lumen of the ETT was checked with the naked eye for any obstruction caused by the external cuff pressure. Results: Neither in tubes that were exposed to ambient temperature (range: -12°C to +44°C) nor in those that were also clamped, visible obstruction by inflated cuffs was detected at any of the two cuff pressure levels. Conclusions: We could not demonstrate a critical obstruction of an ETT by its inflated cuff, neither when the cuff was over-inflated to a pressure of 12 kPa or higher, nor in ETTs that had been exposed to unfavorable storage conditions and significant mechanical stress.
- Soluble triggering receptor on myeloid cells-1 is expressed in the course of non-infectious inflammation after traumatic lung contusion : a prospective cohort study (2011)
- Introduction: The triggering receptor expressed on myeloid cells-1 (TREM-1) is known to be expressed during bacterial infections. We investigated whether TREM-1 is also expressed in non-infectious inflammation following traumatic lung contusion. Methods: In a study population of 45 adult patients with multiple trauma and lung contusion, we obtained bronchoalveolar lavage (BAL) (blind suctioning of 20 ml NaCl (0.9%) via jet catheter) and collected blood samples at two time points (16 hours and 40 hours) after trauma. Post hoc patients were assigned to one of four groups radiologically classified according to the severity of lung contusion based on the initial chest tomography. Concentration of soluble TREM-1 (sTREM-1) and bacterial growth were determined in the BAL. sTREM-1, IL-6, IL-10, lipopolysaccharide binding protein, procalcitonin, C-reactive protein and leukocyte count were assessed in blood samples. Pulmonary function was evaluated by the paO2/FiO2 ratio. Results: Three patients were excluded due to positive bacterial growth in the initial BAL. In 42 patients the severity of lung contusion correlated with the levels of sTREM-1 16 hours and 40 hours after trauma. sTREM-1 levels were significantly (P < 0.01) elevated in patients with severe contusion (2,184 pg/ml (620 to 4,000 pg/ml)) in comparison with patients with mild (339 pg/ml (135 to 731 pg/ml)) or no (217 pg/ml (97 to 701 pg/ml)) contusion 40 hours following trauma. At both time points the paO2/FiO2 ratio correlated negatively with sTREM-1 levels (Spearman correlation coefficient = -0.446, P < 0.01). Conclusions: sTREM-1 levels are elevated in the BAL of patients following pulmonary contusion. Furthermore, the levels of sTREM-1 in the BAL correlate well with both the severity of radiological pulmonary tissue damage and functional impairment of gas exchange (paO2/FiO2 ratio).
- Spike train auto-structure impacts post-synaptic firing and timing-based plasticity (2011)
- Cortical neurons are typically driven by several thousand synapses. The precise spatiotemporal pattern formed by these inputs can modulate the response of a post-synaptic cell. In this work, we explore how the temporal structure of pre-synaptic inhibitory and excitatory inputs impact the post-synaptic firing of a conductance-based integrate and fire neuron. Both the excitatory and inhibitory input was modeled by renewal gamma processes with varying shape factors for modeling regular and temporally random Poisson activity. We demonstrate that the temporal structure of mutually independent inputs affects the post-synaptic firing, while the strength of the effect depends on the firing rates of both the excitatory and inhibitory inputs. In a second step, we explore the effect of temporal structure of mutually independent inputs on a simple version of Hebbian learning, i.e., hard bound spike-timing-dependent plasticity. We explore both the equilibrium weight distribution and the speed of the transient weight dynamics for different mutually independent gamma processes. We find that both the equilibrium distribution of the synaptic weights and the speed of synaptic changes are modulated by the temporal structure of the input. Finally, we highlight that the sensitivity of both the post-synaptic firing as well as the spike-timing-dependent plasticity on the auto-structure of the input of a neuron could be used to modulate the learning rate of synaptic modification.
- Superimposed high-frequency jet ventilation combined with continuous positive airway pressure/assisted spontaneous breathing improves oxygenation in patients with H1N1-associated ARDS (2012)
- Background: Numerous cases of swine-origin 2009 H1N1 influenza A virus (H1N1)-associated acute respiratory distress syndrome (ARDS) bridged by extracorporeal membrane oxygenation (ECMO) therapy have been reported; however, complication rates are high. We present our experience with H1N1-associated ARDS and successful bridging of lung function using superimposed high-frequency jet ventilation (SHFJV) in combination with continuous positive airway pressure/assisted spontaneous breathing (CPAP/ASB). Methods: We admitted five patients with H1N1 infection and ARDS to our intensive care unit. Although all patients required pure oxygen and controlled ventilation, oxygenation was insufficient. We applied SHFJV/CPAP/ASB to improve oxygenation. Results: Initial PaO2/FiO2 ratio prior SHFJV was 58-79 mmHg. In all patients, successful oxygenation was achieved by SHFJV (PaO2/FiO2 ratio 105-306 mmHg within 24 h). Spontaneous breathing was set during first hours after admission. SHFJV could be stopped after 39, 40, 72, 100, or 240 h. Concomitant pulmonary herpes simplex virus (HSV) infection was observed in all patients. Two patients were successfully discharged. The other three patients relapsed and died within 7 weeks mainly due to combined HSV infection and in two cases reoccurring H1N1 infection. Conclusions: SHFJV represents an alternative to bridge lung function successfully and improve oxygenation in the critically ill.
- Deguelin attenuates reperfusion injury and improves outcome after orthotopic lung transplantation in the rat (2012)
- The main goal of adequate organ preservation is to avoid further cellular metabolism during the phase of ischemia. However, modern preservation solutions do rarely achieve this target. In donor organs hypoxia and ischemia induce a broad spectrum of pathologic molecular mechanisms favoring primary graft dysfunction (PGD) after transplantation. Increased hypoxia-induced transcriptional activity leads to increased vascular permeability which in turn is the soil of a reperfusion edema and the enhancement of a pro-inflammatory response in the graft after reperfusion. We hypothesize that inhibition of the respiration chain in mitochondria and thus inhibition of the hypoxia induced mechanisms might reduce reperfusion edema and consecutively improve survival in vivo. In this study we demonstrate that the rotenoid Deguelin reduces the expression of hypoxia induced target genes, and especially VEGF-A, dose-dependently in hypoxic human lung derived cells. Furthermore, Deguelin significantly suppresses the mRNA expression of the HIF target genes VEGF-A, the pro-inflammatory CXCR4 and ICAM-1 in ischemic lungs vs. control lungs. After lung transplantation, the VEGF-A induced reperfusion-edema is significantly lower in Deguelin-treated animals than in controls. Deguelin-treated rats exhibit a significantly increased survival-rate after transplantation. Additionally, a downregulation of the pro-inflammatory molecules ICAM-1 and CXCR4 and an increase in the recruitment of immunomodulatory monocytes (CD163+ and CD68+) to the transplanted organ involving the IL4 pathway was observed. Therefore, we conclude that ischemic periods preceding reperfusion are mainly responsible for the increased vascular permeability via upregulation of VEGF. Together with this, the resulting endothelial dysfunction also enhances inflammation and consequently lung dysfunction. Deguelin significantly decreases a VEGF-A induced reperfusion edema, induces the recruitment of immunomodulatory monocytes and thus improves organ function and survival after lung transplantation by interfering with hypoxia induced signaling.
- Prednisolone as preservation additive prevents from ischemia reperfusion injury in a rat model of orthotopic lung transplantation (2013)
- The lung is, more than other solid organs, susceptible for ischemia reperfusion injury after orthotopic transplantation. Corticosteroids are known to potently suppress pro-inflammatory processes when given in the post-operative setting or during rejection episodes. Whereas their use has been approved for these clinical indications, there is no study investigating its potential as a preservation additive in preventing vascular damage already in the phase of ischemia. To investigate these effects we performed orthotopic lung transplantations (LTX) in the rat. Prednisolone was either added to the perfusion solution for lung preservation or omitted and rats were followed for 48 hours after LTX. Prednisolone preconditioning significantly increased survival and diminished reperfusion edema. Hypoxia induced vasoactive cytokines such as VEGF were reduced. Markers of leukocyte invasiveness like matrix metalloprotease (MMP)-2, or common pro-inflammatory molecules like the CXCR4 receptor or the chemokine (C-C motif) ligand (CCL)-2 were downregulated by prednisolone. Neutrophil recruitment to the grafts was only increased in Perfadex treated lungs. Together with this, prednisolone treated animals displayed significantly reduced lung protein levels of neutrophil chemoattractants like CINC-1, CINC-2α/β and LIX and upregulated tissue inhibitor of matrix metalloproteinase (TIMP)-1. Interestingly, lung macrophage invasion was increased in both, Perfadex and prednisolone treated grafts, as measured by MMP-12 or RM4. Markers of anti-inflammatory macrophage transdifferentiation like MRC-1, IL-13, IL-4 and CD163, significantly correlated with prednisolone treatment. These observations lead to the conclusion that prednisolone as an additive to the perfusion solution protects from hypoxia triggered danger signals already in the phase of ischemia and thus reduces graft edema in the phase of reperfusion. Additionally, prednisolone preconditioning might also lead to macrophage polarization as a beneficial long-term effect.
- The small fibrinopeptide bβ15-42 as renoprotective agent preserving the endothelial and vascular integrity in early ischemia reperfusion injury in the mouse kidney and vascular integrity in early ischemia reperfusion injury in the mouse kidney (2014)
- Disruption of the renal endothelial integrity is pivotal for the development of a vascular leak, tissue edema and consequently acute kidney injury. Kidney ischemia amplifies endothelial activation and up-regulation of pro-inflammatory mechanisms. After restoring a sufficient blood flow, the kidney is damaged through complex pathomechanisms that are classically referred to as ischemia and reperfusion injury, where the disruption of the inter-endothelial connections seems to be a crucial step in this pathomechanism. Focusing on the molecular cell-cell interaction, the fibrinopeptide Bβ15–42 prevents vascular leakage by stabilizing these inter-endothelial junctions. The peptide associates with vascular endothelial-cadherin, thus preventing early kidney dysfunction by preserving blood perfusion efficacy, edema formation and thus organ dysfunction. We intended to demonstrate the early therapeutic benefit of intravenously administered Bβ15–42 in a mouse model of renal ischemia and reperfusion. After 30 minutes of ischemia, the fibrinopeptide Bβ15–42 was administered intravenously before reperfusion was commenced for 1 and 3 hours. We show that Bβ15–42 alleviates early functional and morphological kidney damage as soon as 1 h and 3 h after ischemia and reperfusion. Mice treated with Bβ15–42 displayed a significantly reduced loss of VE-cadherin, indicating a conserved endothelial barrier leading to less neutrophil infiltration which in turn resulted in significantly reduced structural renal damage. The significant reduction in tissue and serum neutrophil gelatinase-associated lipocalin levels reinforced our findings. Moreover, renal perfusion analysis by color duplex sonography revealed that Bβ15–42 treatment preserved resistive indices and even improved blood velocity. Our data demonstrate the efficacy of early therapeutic intervention using the fibrinopeptide Bβ15–42 in the treatment of acute kidney injury resulting from ischemia and reperfusion. In this context Bβ15–42 may act as a potent renoprotective agent by preserving the endothelial and vascular integrity.
- The Early Activation of Toll-Like Receptor (TLR)-3 Initiates Kidney Injury after Ischemia and Reperfusion (2014)
- Acute kidney injury (AKI) is one of the most important complications in hospitalized patients and its pathomechanisms are not completely elucidated. We hypothesize that signaling via toll-like receptor (TLR)-3, a receptor that is activated upon binding of double-stranded nucleotides, might play a crucial role in the pathogenesis of AKI following ischemia and reperfusion (IR). Male adult C57Bl6 wild-type (wt) mice and TLR-3 knock-out (-/-) mice were subjected to 30 minutes bilateral selective clamping of the renal artery followed by reperfusion for 30 min 2.5h and 23.5 hours or subjected to sham procedures. TLR-3 down-stream signaling was activated already within 3 h of ischemia and reperfusion in post-ischemic kidneys of wt mice lead to impaired blood perfusion followed by a strong pro-inflammatory response with significant neutrophil invasion. In contrast, this effect was absent in TLR-3-/- mice. Moreover, the quick TLR-3 activation resulted in kidney damage that was histomorphologically associated with significantly increased apoptosis and necrosis rates in renal tubules of wt mice. This finding was confirmed by increased kidney injury marker NGAL in wt mice and a better preserved renal perfusion after IR in TLR-3-/- mice than wt mice. Overall, the absence of TLR-3 is associated with lower cumulative kidney damage and maintained renal blood perfusion within the first 24 hours of reperfusion. Thus, we conclude that TLR-3 seems to participate in the pathogenesis of early acute kidney injury.